Add simple matching engine

[davidrpugh]

This PR adds a default/generic implementation of a MatchingEngine.

[coveralls]

Coverage decreased (-6.8%) to 90.374% when pulling c3501ec on add-simple-matching-engine into 87b0d8a on develop.

[coveralls]

Coverage decreased (-6.8%) to 90.374% when pulling 21eafc2 on add-simple-matching-engine into 87b0d8a on develop.

[coveralls]

Coverage decreased (-6.8%) to 90.374% when pulling 082e573 on add-simple-matching-engine into 87b0d8a on develop.

[coveralls]

Coverage decreased (-4.04%) to 93.122% when pulling 2ac4ba4 on add-simple-matching-engine into 87b0d8a on develop.